Percent Error Calculator
Compare your experimental measurement against the true theoretical value to find the percent error — the standard accuracy metric for science labs.
What Does This Tool Do?
Enter your measured experimental value and the known theoretical (accepted) value to find the percent error. Used in physics, chemistry and biology labs to assess measurement accuracy.
Key Features
Science-Ready
Standard formula used in all science disciplines.
Working Shown
Formula with substituted values displayed.
4dp Precision
Percent error to 4 decimal places.
Instant
Result on button click.
How to Use
- Enter your experimental (measured) value.
- Enter the theoretical (accepted) value.
- Click Calculate Percent Error.
Frequently Asked Questions
What is the percent error formula?▾
Percent Error = |Experimental − Theoretical| / |Theoretical| × 100. Always expressed as a positive percentage.
Why use absolute value?▾
Percent error measures the magnitude of error regardless of direction. The absolute value removes the sign so only the size matters.
What is a good percent error?▾
Below 5% is generally acceptable in most school and lab experiments. Below 1% indicates a highly precise measurement.